                                                        (unifyc spec rule))
                                                      (if parent (get-head-phrases-of parent index)
                                                          grammar))))
-        debug (log/debug (str "grammar size: " (.size grammar)))
-        debug (log/debug (str "candidate-parents size: " (if (nil? candidate-parents)
+        debug (log/trace (str "grammar size: " (.size grammar)))
+        debug (log/trace (str "candidate-parents size: " (if (nil? candidate-parents)
                                                            "no candidate-parents"
                                                            (.size candidate-parents))))
-        debug (log/debug (str "candidate-parents: " (if (nil? candidate-parents)
+        debug (log/trace (str "candidate-parents: " (if (nil? candidate-parents)
                                                       "no candidate-parents"
                                                       (string/join "," (map #(get-in % [:rule])
                                                                             candidate-parents)))))

there is only one child for each parent, and that single child is the
head of its parent. generate (above) 'decorates' each returned lightning bolt
of this function with complements."
  (log/debug (str "lighting-bolt@" depth ": grammar:" (string/join ", " (map :rule grammar))))
  (let [maxdepth 3 ;; maximum depth of a lightning bolt: H1 -> H2 -> H3 where H3 must be a lexeme, not a phrase.
        index (if (future? index) @index index)
        lexicon (if (future? lexicon) @lexicon lexicon)

            complement-candidate-lexemes (if cached cached (flatten (vals lexicon)))]
        (let [semantics (get-in spec [:synsem :sem])]
          (if (not (nil? semantics))
            (if (not (nil? semantics)) (log/debug (str "  with semantics:" (strip-refs semantics))))))
        (log/trace (str " immediate parent:" (get-in immediate-parent [:rule])))
        (if (map? complement-candidate-lexemes)
          (log/error (str "complement-candidate-lexemes is unexpectedly a map with keys:" 
